Reppel P D, Böning K, Walter M
Fachbereich Zahn-, Mund- und Kieferheilkunde der Freien Universität Berlin.
Dtsch Zahnarztl Z. 1991 Nov;46(11):756-8.
In a clinical study the accuracy of fit of 82 crowns manufactured with the Procera-system (duplication milling/spark erosion) was investigated. The average marginal space width was 71 microns. Roughness of eroded surfaces was found to be similar to that of coarsely ground metal. Below the eroded areas a zone of increased hardness with a width of approximately 20 microns was demonstrated.
